#include <stdio.h>
#include <math.h>
void main()
{
	int sign=1;
	float n=1,t=1,pi=0;
	while(fabs(t)>1e-6)
	{
	pi+=t;
	n+=2;
	sign*=-1;
	t=sign/n;
    }
    pi=pi*4;
	printf("PI=%10.6f\n",pi);
}
